Police arrested a man who allegedly exposed himself to a girl in San Mateo on Monday evening.

At 5:55 p.m., the 16-year-old victim was walking west up the roundabout leading to the pedestrian overcrossing at Monte Diablo Avenue and Amphlett Boulevard when she noticed the man masturbating while exposing himself to her, police said.

When the victim arrived at home, she contacted police and reported the incident, police said.

Officers immediately responded to the area and searched for the suspect. They later located and identified the man as 35-year-old Christian Morales, police said.

Police said they knew Morales because of similar prior arrests. He is also a registered sex offender, police said.

Morales was arrested and booked into San Mateo County Jail on suspicion of indecent exposure and annoying or molesting a child under 18 years old, police said.

Anyone with further information about this case or Morales is asked to contact police at (650) 522-7700.